Mercury jet switch and rotor therefor



Jan. 16, 1962 R. J. MATTHEWS MERCURY JET swITcx-x AND RoToR THEREFOR Filed Dec. 7. 1959 ATTORNEYS 3,017,468 MERCURY .YET SWITCH AND RTR THEREFOR Robert I. Matthews, Menlo Park, Calif., assxgnor to American Radiator & Standard Sanitary Corporation, New York, N.Y., a corporation of Delaware Filed Dec. 7, 1959, Ser. No. 857,975 4 Claims. (Cl. 200-32) This invention relates to and in general has for its object the provision of a mercury jet switch of the character disclosed in the Davis et al. Patent No. 2,782,273 of February 19, 1957.

Switches of this type include a stator provided with a central mercury supply w-ell and with a circle of equally spaced contact pins; a rotor pro-vided with a mercury jet nozzle directed towards said contact pins, and `a pump associated with said rotor for pumping a stream of mercury from said well to said nozzle. During each revolution of the rotor the mercury jet from the nozzle successively contacts each of the contacts and this can be made to serve as a switch for successively closing electrical circuits associated with the contact pins.

Although electrical conducting iiuids other than mercury can be used for this purpose, mercury has been found to be more practical than other fluid conductors.

However, the use of mercury has given rise to one problem which to date has not been satisfactorily overcome. During the operation of a rotary mercury jet switch, a heterogeneous mixture of scum and mercury particles forms which, if not disposed of or trapped, results in plugging the jet nozzles. This scum is comprised of mercury oxides of amalgams of mercury with other metals, and of organic materials originating in `the bearing lubricants.

Attempts to solve the mercury scum problem by using sterile assembly procedures and chemically pure mercury have been noteworthy largely for their failures, and attempts to effect a separation of the scum from the Inercury have been only partially successful and merely delay the time of shutdown.

More specically, the object of this invention is the provision of a mercury jet switch including a rotor provided with an upwardly and outwardly extending scumreceiving pocket having its mouth located at or just beneath the mercury level and including an upwardly and outwardly extending mercury supply pump conduit communicating at its upper end with jet nozzle of the rotor and having its intake end disposed substantially below the mercury level. As a result of this construction and due to the fact that the mercury scum is lighter than the mercury, the scum is forced into the scum pocket under the action of centrifugal force and there adheres to the pocket walls. By making the surface area of the scum pocket suiiiciently large, the scum capacity of the pocket can be made coextensive with the life of the switch. Since the scum can be pocketed or trapped substantially at the rate at which it is formed, and since the mercury supplied to the jet nozzle is taken from the mercury well at a point substantially below the scum level, the inclusion of scum in the nozzle supply is avoided and plugging of the nozzle is obviated.

Still another object of this invention is the provision of a switch of the character above described wherein mercury is supplied to the jet nozzle by a tube extending through the scum pocket.

Still another object of this invention is the provision of stator and rotor components which can be readily stacked to form a multiple unit switch.

The invention possesses other advantageous features, some of which, with the foregoing, will be set forth at length in the following description where that form of 3,i7,468 Patented Jan. 16, 1962 the invention which has` been selected for illustration in the drawings accompanying and forming a part of the present specification is outlined in full. In said drawings, one form of the invention is shown, but it is to be understood that it is not limited to such form, since the invention as set forth in the claims may be embodied in other forms.

Referring to the drawings:

The figure is a vertical mid-section of a multiple-unit mercury jet switch embodying the objects of my invention.

The embodiment o-f my invention as illustrated in this ligure includes a plastic base or motor adapter 1 arranged to be seated on the end of an electric motor not shown. Formed in the adapter 1 is a tapered coaxial bore 4 for the reception of the motor shaft 5, the switch shaft and a coupling for joining the -two shafts, all of which will be presently described in greater detail. Also provided in the adapter 1 are diametrically opposed openings 6 for access to the coupling.

Formed on the upper end o-f the `adapter 1 is an annular land 7 provided with a step 8 and with an annular sump 9.

Seated on the land 7 is the downwardly extending annular foot 11 of a lower plastic stator section 12. Formed on the stator section 12 inwardly of its foot is an annular depending, tapered guide ring 13 arranged to seat on the step 8 and spaced inwardly from the foot 11 so as to define therewith an annular channel 14 for the reception of an O ring 15. The center of the bottom section 12 forms an upwardly extending inclined hub 16 terminating at its upper end in a shaft bore 17. The lower central surface 1S of the lower stator section is upwardly arched or domed and, as will presently appear, with respect to the next succeeding switch unit serves as a dome or ceiling for the rotor compartment. However, surface 18 0f the lowermost stator section does not function in this manner, for no rotor is included between this section and the adapter 1.

Circumscribing the hub 16 is a downwardly converging annular mercury supply sump or well 21 merging at its periphery with an inclined drain bottom 22. The bottom 22 in tu-rn merges with a vertical wall 23 and the wall 23 terminates in a fiat land 24 corresponding to the land 7 of the adapter 1.

Molded in the lower stator section 12 are a plurality of inverted U-shaped wire contactors 26. The inner leg 27 of each contacter extends downwardly into the dome 18 of the stator section and hereafter will be referred to as a contact pin. The outer end 28 of each contacter depends into an annular peripheral channel 29 formed by a radially extending flange 31 of the adapter and an overhanging radially extending iiange 32 of the lower stator section 12. The contactor leg 28 serves as an electric terminal and will hereafter be referred to as such. The contactors 26 are arranged in a ring about the lower stator section, and of such number and spacing to provide the desired pattern of circuit on time when the switch is in operation. However, the contactors should not be so closely spaced that the mercury jet, as it rotates within the ring of contact pins 27, impinges simultaneously on two adjacent pins.

Formed on the periphery of the stator fiance 32 is an annular tapered notch 33 and surrounding the adapter and stator flanges 31 and 32 is a metal clamping ring or band 34, channel-shaped in cross-section. The ends of the band 34 terminate in a conventional clamp 35 for cinching the band around the adapter and the lower stator section 12.

Extending radially through the stator section 12 is a small bore 36 for introducing mercury into the supply Well 2.1 and threaded into the outer end of the bore 36 is a screw plug '37. Circumscribing the lower part of the stator hub 16 and disposed within the bottom of the well 21, so as always to be in contact with a body 38 of mercury maintained therein, is a stiif wire ring 39. Connected to the ring 39 is a stiff wire lead 41 passing over the upper surface of the mercury well. Embedded in the lower stator section 12 is an internally threaded connector sleeve 42 provided at its lower end with a diametral hole for the reception of the outer end of the lead 41; threaded vinto the sleeve 42 is a set screw 43 for locking the lead 41 in place, and threaded into the outer end of the sleeve 42 is a terminal screw 44. It is to be here noted that the elements 41, 42 and 43 are here illustrated only in connection with the next succeeding stator section 12a and its associated rotor 51a and are indicated more speciiically by the reference numerals 41a, 42e and 43a appearing in the upper left corner of the drawings. As later explained, the two rotors and two stators illustrated are identical in construction and function.

Mounted over the stator section 12, and held positively spaced therefrom by means which will be presently described, is a plastic rotor 51 provided with an inwardly extending ange 52 overhanging the lower stator section hub 16. The inner wall 53 of the rotor 51 is slightly downwardly divergent and follows the inclined contour of the hub 16. The upper wall 54 of the rotor is generally complementary to the lower wall of the lower stator section 12. The outer wall 55 of the rotor 51 is of truncated cone conguration and has substantial clearance with the opposed inclined wall of the stator section 12. Formed in the bottom of the rotor is an annular countersink or recess 56 disposed immediately above the contact ring 39 and located well below the mercury level 57. Provided in the -inclined inner wall 53 of the rotor is an annular, radially extending mercury slinger groove S for entrapping any mercury which may creep up the channel formed between the hub 16 and the rotor wall 53. A radial hole connects the mercury slinger groove 58 to the rotor outside surface 55, thereby providing an egress route for mercury caught in the slinger groove to the sump 21. Screwed to the rotor is an annular plastic drain gutter 59 provided with an overturned flange 61. Extending through Vthe gutter 59 at a point over the inclined drain bottom 22 of the lower stator section 12 is a mercury drain hole 62. Fixed to the periphery of the rotor '51 is a mercury jet nozzle 63 in radial or chordwise alignment with the rotor iiange 51 of the rotor gutter 59. Although from a functional standpoint only one such nozzle is required, to maintain the rotor in dynamic balance it should be symmetrically constructed with reference to its axis and therefore provided with a second and dummy nozzle 64 diametrically opposite the active nozzle 63. rFormed in the rotor 51 are two diametricallv opposed, outwardly inclined, upwardly converging mercury scavenging cavities 65. The lower end of each cavity is open and communicates with the annular rotor recess 56, whereas its upper end is closed and terminates short of the jet nozzle 63. Extending through the rotor 51, but not n-ecessarily within the cavities 65, is a mercury feed tube 66 communicating at its lower end with the annular recess 56 and at its upper end with the nozzle 63. Preferably the lower end of the tube 66 is bent horizontally in the direction of rotation of the rotor so as to function as a mercury scoop. Since the tube 66 is outwardly inclined, it functions as a centrifugal pump when the rotor is rotating and pumps an unbroken stream of mercury to the mercury jet nozzle 63. A similar but dummy and diametrically opposed construction should be provided on the opposite side of the rotor so as to maintain the rotor in dynamic balance.

Mounted over the lower stator section 12 and the rotor 51 is an intermediate stator section 12a in all respects identical to the section 12, and associated with the section V12a is an upper rotor 51a likewise identical in all respects to the lower rotor 51a. For purposes of convenience, the parts section 12"4 and rotor 512L have been designated by the same reference numerals, but qualified by the letter a.

From an inspection of the relative positions of the stator section 12 and its associated rotor 51, it will be seen that the contact pins 27 E are disposed between the mercury jet nozzle 63 and the drain gutter flange 61, and that consequently each of the contact pins 27a will be successively contacted by the stream of mercury emanating from the jet nozzle 63 upon rotation of the rotor. The mercury, after hitting the contact pins or passing between them, hits the ange 61, passes through the drain hole 62 and then drains into the mercury supply well 21. Since any mercury scum formed is lighter than the mercury, it rises to the top of the body 38 of mercury. Since the rotor cavities 65 are inclined, they function as centrifugal pumps and consequently `the mercury scum moves upwardly in the cavities 65 and `adheres to their surfaces. The surface area of the cavities is sufficient to retain whatever scum is formed during the normal operating life of a switch of this character.

Each of the terminals 28a is connected with an insulated lead 67a through a plug connector 68a, land the leads 6'7a are made up into a cable 69a extending through a grommet 70a mounted in the clamping band 34a.

Mounted over the intermediate stator section 12a and the intermediate rotor 51a is a cap 71, the lower face 4of which is contoured identically with the contour of the lower face of the intermediate stator section 12a except that instead of being provided with a hub it is formed with a central bore 72 and a counterbore 73. For purposes of convenience, the elements of the cap 71 corresponding to the elements of the stator sections have been indicated by corresponding reference numerals qualified by the letter b.

Mounted in the counterbore 73 is a bearing assembly 74 held in place by a snap ring 75. Likewise mounted in the motor adapter 1 is a bearing assembly 76 held in place by a snap ring 77. Journaled in the -two coaxial bearing assemblies 74 and 76 is a shaft 78 formed with steps 79, S1 and 82.

The step 79 has a running clearance with shaft seat 17 of the lower hub 16, and its upper end underlies and serves as a support for the rotor ange 52. Circumscribing the step 81 is a spacer sleeve 83 having an outer diameter equal to the outer diameter of the shaft step 79. The lower end of the sleeve 83 seats on the rotor ilange 52 and is keyed thereto by a pin 84. The upper end of the sleeve serves as a support for the overhang-ing iiange 52a of the upper rotor 51a and is keyed thereto by a pin 84E. Tightly screwed over step S2 is a nut 85 serving -to lock the two rotors 4to the shaft step 79 and made a rigid integral structure thereof.

Slipped over the two adjacent ends of the motor and switch shaft is a composite coupling 86 consisting of a central insulating plug 37 provided with a central radial ilange 38 bonded to upper and lower sleeves 89 and $1. Extending through the upper sleeve S9 is -a set screw 92 engaging the lower end of the switch shaft, and similarly threaded through the lower sleeve 91 is a set screw 93 engaging the motor shaft 5. Both of these s et screws are accessible through the adapter openings 6.

Closing the upper end of bearing assembly bore 73 1s an inverted metal cup 95.

As a result of the complementary upper and lower contours of the rotors and stator sections, any desired number of these units can be stacked on each other to form a multiple-unit, multiple-pole switch.

After the switch elements have 4been assembled and locked together, mercury is supplied to the mercury well of each unit through the bores 36 to the level 57 slightly below the outlet of the bore 36. This having been done, the leads 67a and 44 can be connected as desired to the proper circuitry. The electrical path through the switch proceeds from each lead 6"!"a through the connectors 26a, through the mercury jet extending between the contact pins 27a and the jet nozzle 63, down the stream of mercury filling the tube 66, through the mercury in the mercury well 21 to the wire ring 39 and up the lead 41 to the terminal 44. As a result of this the 4terminal 44 is placed in communication with each of leads 67a once during each revolution of the rotor 51. The operation of the switch should otherwise be clear from the above description thereof.

I claim:

1. A rotary jet switch comprising: a central mercury supply well; -a rotor provided at its lower end with an annular mercury-confining recess and arranged to be yimmersed in a body of mercury contained in said well; a mercury scum-receiving cavity formed in sa-id rotor extending upwardly and outwardly from the upper face of said conning recess, said cavity being closed `at its upper end; a mercury jet nozzle provided on said rotor substantially above said well, and a mercury conduit provided in said rotor extending upwardly and outwardly from said Iannular recess, the lower end of said conduit being in communication with said recess Iat la point below the upper portion thereof and having an intake facing the direction of rotation of said rotor and the upper end of said conduit being in communication with said nozzle.

10 conduit being in communication with said recess at a point below Ithe upper end of the scum-receiving cavity and its upper end vbeing in communication with said nozzle.

References Cited in the le of this patent UNITED STATES PATENTS 866,289 Luschka Sept. 17, 1907 2,782,273 Davis et al. Feb. 19, 1957 2,822,513 Bohn et al. Feb. 4, 1958 2,895,060 Dorn July 14, 1959 FOREIGN PATENTS 338,968 Germany July 9, 1921 367,622 Germany Jan. 24, 1923 453,080 Great Britain Sept. 4, 1936 

